From: Yohanes Santoso <ysantoso-rubytalk@...>
Date: 2005-04-13T15:09:02+09:00
Subject: Re: ability to run finalizers at a given point of a program?

Guillaume Cottenceau <gcottenc@gmail.com> writes:

> What version of Ruby are you running? With your example I can see:
>
> *** constructor
> Foo was out-scoped.
> Gc was run.
> *** pseudo-destructor

$ ruby -v
ruby 1.8.2 (2004-12-06) [i386-linux]

# Guillaume Cottenceau's version

$ ruby /tmp/guil.rb
*** constructor
Foo was out-scoped.
Gc was run.
*** pseudo-destructor

# TS' version

$ ruby /tmp/ts.rb
*** constructor
Foo was out-scoped.
*** pseudo-destructor
Gc was run.

So, I am getting the same result ts was getting.

> What difference do you pretend your program is making with mine?

The difference is in this:

(your version):
def scopeme
    foo = Foo.new
    ObjectSpace.define_finalizer(foo, proc { puts "*** pseudo-destructor" })
end

That block captures foo as well. As a result, that instance will never
be unreferenced, and thus never going to be GC'ed until the program
ends.

OTOH, ts' version:
class Foo
   def self.final
      proc { puts "*** pseudo-destructor" }
   end
end

def scopeme
   foo = Foo.new
   ObjectSpace.define_finalizer(foo, Foo.final)
end

Notice that the finalizer block does not capture the Foo instance.

YS.